Update README.md

Author: jaw111

packages/aws-cdk-lib/aws-sns/README.md

@@ -121,11 +121,13 @@ declare const fn: lambda.Function;
 
 // Lambda should receive only message matching the following conditions on message body:
 // color: 'red' or 'orange'
+// store: attribute must not be present
 myTopic.addSubscription(new subscriptions.LambdaSubscription(fn, {
   filterPolicyWithMessageBody: {
     background: sns.FilterOrPolicy.policy({
       color: sns.FilterOrPolicy.filter(sns.SubscriptionFilter.stringFilter({
         allowlist: ['red', 'orange'],
+        store: sns.SubscriptionFilter.existsFilter(false),
       })),
     }),
   },